NO. 8 MORPHOLOGY OF INSECT SENSE ORGANS SNODGRASS 75 



vestigators. Certainly it has no relation to the lateral eyes of other 

 larva, and must be regarded, therefore, either as a primary frontal 

 ocellus persisting in a larval stage and moved to the side of the 

 head, or as an independent development. 



POSTSCRIPT 



Much has been omitted from the foregoing accounts of the struc- 

 ture of the sense organs and the nervous system of insects that a 

 complete discussion of the subjects involved should contain, though 

 the writer hopes that no recorded information has been overlooked 

 or withheld that would weaken the general statements given, or that 

 might have an important bearing on the matters discussed. Many 

 of our present ideas on insect morphology are still in a controversial 

 stage, and undoubtedly some current generalizations will be found 

 to be based on a too limited knowledge of the facts, considering the 

 great diversity in all the structural parts of insects. The writer, 

 however, who undertakes to present a review of the facts known in 

 any branch of insect anatomy must remember that his offering will 

 be of value chiefly to the student or to the practical entomologist 

 looking for concise, information, and who is likely not to be interested 

 in long discussions on subjects still under dispute among specialists. 



On the other hand, a reviewer, through his desire to have his sub- 

 ject matter well classified, or to make it appear as complete as pos- 

 sible, may err in presenting it in a form more concise and more defi- 

 nite than is warranted by the facts. This is exemplified in the treat- 

 ment of insect sense organs as commonly given in entomological 

 texts, where each known group of organs is assigned to a special 

 sense, as is done in text books on human anatomy, while from the 

 writings of specialists it would appear that almost nothing is settled 

 concerning the functions of the insect organs. The condition, how- 

 ever, is not one of chaos. The last twenty-five years has seen a vast 

 increase in our knowledge of insect structure in general, and in par- 

 ticular of the sense organs, but by this very increase of printed in- 

 formation the work of assembling and reviewing it has become a 

 task that can scarcely be done except by one who has all his time 

 to devote to it. We must note with satisfaction, however, the increas- 

 ing importance being given to morphology by the authors of our 

 present general texts on entomology, and it is clear that the painstak- 

 ing work of recent students will give to the subject of insect anatomy 

 in the future a higher scientific standing than its adherents have here- 

 tofore been able justly to claim in its behalf. 



